Amazing Barn Find!!

Check out the sludge trap before starting the engine, it will mean a total strip down of the engine, but in the end it will be worth it, engine bearings may need replacing due to non use, if in doubt ask an expert, I'm not an expert, however have owned too many bonnies over the years to know that these thing do need looking at, could save you $$$$$$$.

Just advice, take it or leave it...

p.s. always upgraded where possible to three phase alternator, rectifier etc, fitted halogen headlight, and boyer electronic ignition set up.

Happy riding.

Advice well taken! I have no history on this bike (except for the fact its been sitting since 2001) and it really needs to be gone through. It is REALLY hard to start and it will probably need a top end at least, so as long as I'm doing that I might as well tear it down all the way and check the sludge trap, as you mentioned.

I picked it up Saturday, washed off the dirt, and already have found some goofy stuff. All in all its not too horrible, just about what I thought, and it has some good stuff too. All the chrome appears to be good, it has a new chain and sprockets on it, new tires and tubes that hold air. It needs a bunch of stuff like a turn signal lense, (they actually work), fork seals, headlight bulb... yada yada .

Its a project. Its a cool old bike. I like it...

Oh... I forgot to ask... Do you have any three phase alternators laying around ??

The only one I ever had or have seen was on an electric start Commando I had years ago.

That would be nice to have one on the Bonnie.... I wonder if they pop up on Flea Bay?

Sluddddggggeeee

I gotta ask a question. What is a sludge trap? I had a number of pre-Hinkley twins and I went to an old shop manual and looked and the only thing I can ascertain as a sludge trap would be the lowermost area in the main case where the crank cheeks swing.

You found it Flip.

The sludge trap is called the 'oil tube' in workshop manuals, it is situated in the crankshaft
on the right main bearing side, it is held in place via a screwed plug, this plug can be hard to extract.

Those were the days

Back then, even expensive oil was paraffin based and would cause 'sludge'. Now day's with synthetic lubricants, 'sludge' is a thing of the past. Even cheap oil like Penzoil and Quaker State have reduced the paraffin levels so when you pull a valve cover on an emissions engine you can see the overhead instead of a gob of dark brown jelly.

There is still plenty of sludge ( and other kinds of dirt and crud) to be found in something like an old Bonnie. I'm pretty sure mine has never seen any kind of synthetic oil ever.

I may be wrong but I think the sludge trap in the crank was supposed to be a last defense against particles that were trying to find their way to the big end bearings and possibly plugging up the small oil ways or lodging in the plain bearings themselves. Centrifical force captured these particles and kept the world safe. A good plan if the bike is used regularly and the oil is changed often. I don't think they counted on the bikes sitting for ten or fifteen years between starts. That old dino oil starts to re- refine itself into stuff we don't want to think about.

I've cleaned out a few old sludge traps. It usually requires a large bench vise (to hold the crank), some heat and a quality impact driver. Those plugs laugh at Chinese tools. Better go see your Snap On man. I've done a Norton or two and several BSA's. For some reason those old BSA's really worried me with that plain crank bearing on the timing side, those things will blow up all by themselves without any help from crap in the sludge trap

Question

Tom:

I have a nagging question. Is that the stock seat? I never remember Triumph doing the stitch design on the top of the seat.

I have got an urgent and potentially ... nagging reply. And that is that Tomo's barn discovery is a 1979, NOT a 1978 T140 Bonnie. Here's why:

1. Side panels. The 1978 version bolted-on logo read:

BONNEVILLE
750

The 1979 version (except the very limited-edition T140D, but that's another story) had a rectangular badge that just read:

BONNEVILLE

2. Finish: A black tank with red "wings" (Are they actually red, under the chicken shack manure... oops... dust , Tomo???) definitely denotes the '79 model-year for US-bound machines.

As far as the "stitched" seat is concerned, Flip, I 'd sumbit (argue?) that it first appeared on the 1977 limited-edition T140J "Silver Jubilee Bonneville" (after Queen Elizabeth's 25th Jubilee Year) in BLUE vinyl .

It was then fitted to the rest of the line in late '78, soberly resorting to BLACK vinyl again. And the numerous leftovers became standard equipment for the '79 season, at least on US "export models".

God Save The Queen. Jamie